A port is an endpoint of communication in an operating system. While the term is also used for hardware devices, in software it is a logical construct that identifies a specific process or a type of service.
Port numbers are assigned in various ways, based on three ranges:
System Ports (0-1023), User Ports (1024-49151), and the Dynamic and/or Private Ports (49152-65535);

The Well Known Ports are assigned by the IANA and on most systems can
only be used by system (or root) processes or by programs executed by
privileged users.
Ports are used in the TCP [RFC793] to name the ends of logical
connections which carry long term conversations. For the purpose of
providing services to unknown callers, a service contact port is
defined. This list specifies the port used by the server process as
its contact port. The contact port is sometimes called the
"well-known port".
To the extent possible, these same port assignments are used with the
UDP [RFC768].
The range for well-known ports managed by the IANA is 0-1023.
DYNAMIC AND/OR PRIVATE PORTS
Registered Ports are those from 1024 through 49151.
The Dynamic and/or Private Ports are those from 49152 through 65535